Dillon County, SC Insulation Payback
Attic insulation payback for Dillon County, SC
DOE classifies Dillon County as climate zone 3, mixed-humid — a genuine mix of cold winters and humid summers, with neither one dominating the bill. Its recommended attic R-value for bare joists is R-49. For an attic around 1,000 square feet, closing the gap from R-2 to R-49 costs around $2,820 and saves an estimated $1,041 a year — payback in roughly 2.7 years. Hard to find a home improvement with a faster payback than this.
Where the savings come from
Of that, about $730/year comes from reduced heating and $311/year from reduced cooling load through the ceiling. Dillon County beats 20% of the counties in this 3,162-county dataset on estimated insulation savings. Among the 690 counties DOE places in zone 3, Dillon County ranks 380th. Against South Carolina's own average of $1,016/year, Dillon County runs 2% above that.
Where these numbers come from
The heating and cooling degree days behind this estimate — 2,752 HDD and 1,950 CDD (base 65°F, 1991-2020 normals) — come from DILLON, SC US, the nearest NOAA station with published normals, 1.7 miles from Dillon County's center. By total degree days, Dillon County sits at the 17th percentile nationally. DOE also classifies Dillon County as moisture regime A (humid) - ask a local contractor whether that changes the vapor-barrier approach for this job.
The smaller top-up scenario
A shallower starting point changes the math: with R-11 already down, only the gap to R-38 needs filling, at roughly $1,620 for an estimated $140/year saved (~11.6-year payback). It is close - the payback only just fits a reasonable timeframe.
Quotes and materials for this job
Real bids depend on how easy the attic is to reach and whether old insulation needs removing first, so treat $2,820 as a starting estimate for a Dillon County job, not a quote. Expect at least a $600 minimum charge from most contractors.
More on how this was built
Nothing here is a guess: the methodology guide names the DOE climate map and NOAA station data behind every number on this page. See the DIY vs. contractor guide for whether a job this size is realistic to do yourself.